2007-10-31_REVISION - M2006080 (2)

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V. TECHNICAL SPECIFICATIONS 5.01 Slurry Wall Alignment The proposed slurry wall alignment is shown on Sheet 102. The alignment was determined by Loveland Ready Mix. The alignment length is approximately 7,300 linear feet. 5.02 Slurry Wall Depth and Width Based on test boring information the total depth of the slurry wall along the alignment is estimated to range from 33 to 47 ft bgs, with an average depth of 38 ft bgs. The slurry wall width shall be a minimum of 30 inches. The depth to the top of bedrock and the bottom of key shall be measured in intervals of no less than 20 feet. 5.03 Slurry Wall Key The general bedrock conditions consist of approximately 7 ft to 18 ft (average of 13 ft) of fractured rock overlying massive rock. The fractured rock is relatively permeable with results of 10-3 and 10~ cm/sec which is not suitable for a slurry wall "key". The massive rock had permeability results of 10-5 to 10"6 cm/sec which is permeability consistent with a "key" for the slurry wall. Therefore, to reduce seepage at the base of the slurry wall, the wall shall be installed 0 to12 inches into massive bedrock, unless otherwise directed by Lyman Henn due to bedrock conditions. The massive bedrock is expected to be very difficult to excavate and excavator refusal is expected to occur within several inches of penetration. The estimated depth to the top of massive bedrock is depicted on Sheets 104 and 105, and summarized on Table VI. Additional excavation through weathered bedrock may be required below these depths until a 0 to 12 inch key into competent bedrock is established, depending on field conditions. 5.04 Slurry Wall Excavation The slurry wall shall be constructed using the continuous slurry trench method. The slurry trench method involves excavating a trench and stabilizing the excavation with viscous bentonite slurry. Trench stability is achieved by establishing a slurry elevation several feet above the groundwater elevation such that a positive hydrostatic slurry pressure exists in the trench and acts against the trench walls to provide stability. The slurry level shall not be allowed to drop more than 2 feet below the working platform. It is anticipated that the soil and fractured rock along the slurry wall alignment can be excavated primarily with specially equipped large excavators. However, the massive bedrock is expected to be very difficult to excavate and excavator refusal is expected to occur within several inches of penetration. 5.05 Bentonite The bentonite slurry shall have the following in-trench characteristics: ^ Marsh funnel viscosity > 40 seconds; and ^ Unit weight at least 15 pounds per cubic foot less than the backfill. G:\pROIECTS\IO'IO_I.0001nvclavd Ready Mu Shirty WaI1~R Records avd Cortespovdrnce\R.11 Reports\Fiva151urty Wall Design Report.doc